Some conventional dental handpieces are provided with lighting means for illuminating treatment site in the oral cavity of a patient during treatment. Light sources employed as such lighting means are predominantly high intensity halogen lamps.
FIG. 2 illustrates such a conventional handpiece 30 having turbine head 10' and a coupling 10". Halogen lamp 40 is disposed inside the coupling 10", and the light emitted by the lamp 40 is transmitted through a light transmitting fiber 42 such as rod fiber or glass fibers in the turbine head 10' to light projecting window 41 located in head 11 or neck 12 of the turbine head 10', which is to be positioned close to the treatment site in use, for illuminating the treatment site.
However, halogen lamp 40 has the following drawbacks:
(1) Halogen lamps employ filaments to generate light from electrical current passing therethrough. However, not a little portion of the electrical current is also converted to heat. Thus, the conversion efficiency from electric current to light is low, which increases consumption of electric power. In addition, the heated filaments endanger the safety of the handpiece.
(2) Filaments tend to rupture due to the rotational vibration caused by a micromotor in the dental handpiece or high speed rotation mechanism in an angle type handpiece, or due to cutting vibration generated in cutting the treatment site. Therefore, filaments in the halogen lamps have low shock resistance and thus short service life.
(3) The halogen lamps and the light transmitting fibers are not durable against steam when sterilized in an autoclave. Therefore, the lamps and the fibers require frequent replacement and repair, which causes unreasonably high cost.
(4) The halogen lamps cannot be disposed in the head or neck of the turbine head for direct illumination of the treatment site, since the size of the lamp cannot be decreased sufficiently for this arrangement. Accordingly, expensive light transmitting fibers should be used for light transmission, which makes the handpiece structure complex. Further, the light emitted by the halogen lamp attenuates physically through the light transmitting fibers by more than 20% .
In the field of display device, optical semiconductor device is often used as an optical display element due to its quick on-off response. Further, the optical semiconductor device is also used as a light source for various measurements. However, there has never been proposed to use an optical semiconductor device as lighting means in a dental handpiece.